The Web and dating, it seems, are a match made in heaven. Americans will spend nearly half a billion dollars on Internet dating services this year, according to JupiterResearch. "People spend more on online personals than any other form of online content," says Nate Elliott, Jupiter's Internet-dating analyst. "By 2009, we expect revenues to reach $623 million." Clearly, the leading sites stand to make a fortune, and few are raking it in like eHarmony.com.

A recent study by Comscore, another Internet research firm, estimates that eHarmony had nearly 1.5 million unique visitors this past June, making it the Web's tenth most popular dating site. And even though the market leader, Yahoo! Personals, pulled in a whopping 6.5 million visitors and Match.com garnered more than 4 million, eHarmony ranks first when it comes to attracting new dollars. Over the past three months, says Comscore, the site accounted for 36 percent of the many millions spent by first-time Internet daters, more than any competitor.

For one, eHarmony is drawing an unusually large number of new users by advertising heavily on the big three national radio networks and top-tier cable television. But it's also charging a premium for its services. Whereas Yahoo! charges almost $20 for a monthly subscription and Match.com ups the price to almost $25, eHarmony asks for nearly $50. Unlike services of the past, the site purports to use "scientifically proven" psychological profiling to make matches.

eHarmony was founded by Neil Warren, a Pasadena psychologist. Over the past 37 years, he's scrutinized the relationships of more than 7,000 patients and performed what he likes to call "divorce autopsies" on failed marriages. It's his belief that three out of every four marriages fail simply because the couple was a poor match from the very beginning. "Most marriages," he says, "are in trouble the day they start."

So, more than a decade ago, he set out to teach people how to choose a spouse properly. Initially, he and his new company tried to get his message out on books and videotapes, but the company didn't really take off until he decided to bring his message to the Web. "We pretty quickly came to the conclusion that moving our business on the Internet made distribution so much more feasible."

eHarmony went live on August 22, 2000. Rather than letting singles post and browse online personals at random, it asked users to fill out a 436-item psychological questionnaire and, using the results, actively matched them with compatible mates. By that December, the site had 20,000 registrants. Now it's up to 4.5 million, with around 10,000 signing up each day.

Jumping to the Web was undoubtedly the right move, but ironically, eHarmony's large audience was built mostly with traditional advertising. Warren says that with a premium service like eHarmony, you need long-format radio and television ads to get your message across. "Online advertising is hard because you have to try to differentiate your product in a short number of words, and our product needs differentiation," he says.

Is eHarmony really doing something above and beyond the everyday dating site? It does take great pains to make appropriate matches. Custom-built with enterprise Java tools and running on Resin, an open-source application, the site takes the answers to your questionnaire and stores them in a Microsoft SQL database as a "psychological profile." Then, on a nightly basis, using a series of algorithms, it compares your profile with the profiles of all other active users (currently, around 900,000 people are active at any given time) and spits out a list of people with similar tastes, characteristics, attitudes, and values.

Once this process is complete, the site uses SendMail, an open-source e-mail gateway, to alert you to new matches, and you're able to contact these peopleand only these peoplevia an anonymous communication tool back on the site.

As the company's ads attest, many have found love using this system, but it may backfire with others. "I found the whole process rather New-Agey and overly reliant on religious beliefs," says Peter McLaughlin, 37, a veteran online dater from Yonkers, New Yorkthough he did start one successful, if short-lived, relationship on the site and signed up for a second month of service. Whatever the case, eHarmony has undoubtedly built a successful Internet business. People are willing to pay premium prices for online services. You just have to convince them that the extra dough is money well spent.